It has been determined that certain structures produced from asbestos and cement, when in continual contact with water, are destroyed over a period of time due to the solubilization of the water soluble constituents of hardened cement, which of course weakens the bonding material. This effect has been of chief concern particularly in those industries which utilize water in great quantities, for example, the cooling water industry. Asbestos-cement compositions have been used to produce boards which are in turn used as fills in cooling water towers. Asbestos-cement fills are being utilized to great extent in the electric utility industry primarily because of economics.
In the past the cooling systems which contain asbestos-cement board fills have experienced problems from standpoints of structure degradation, bowing and softening and ancillary problems resulting to the cooling water train due to the existence of the components of asbestos and cement which have dissolved or broken down and which could, if present in sufficient quantities, deposit on heat transfer surfaces. The overall effect of the deposition thus is to decrease efficiency of the operation, resulting in economic loss.
At the present time, the electric utility industry utilizes corrosion resistant alloys in conjunction with coatings to minimize corrosion. Cooling water velocities are chosen very critically to control deposits. For the most part, no chemical treatments for corrosion or deposition are generally used in this industry. In certain power stations, no chemical treatments are utilized because of environmental restrictions. Accordingly, until the discovery of the present conditions, i.e., degradation of asbestos-cement structures, the electric utility industry required little or no chemical treatment.